CORROSION RESISTANCE AND ANTI-CORROSION PERFORMANCE OF OVERLAPPING LAYERS BETWEEN Al-5Mg THERMAL SPRAYED COATING AND HEAVY DUTY PAINT COATING WITH A CROSS-CUT DEFECT

Abstract

 The purpose of this research is to clarify the characteristics of corrosion resistance and anti-corrosion performance of overlapping layers between Al-5Mg thermal sprayed coating and heavy duty paint coating in a high corrosive environment. Accelerated exposure test was carried out on specimens with overlapping layer, and the cross-cut defect were introduced into specimens to form a steel based-exposed portion. In addition, the AC impedance measurements, glossiness tests on the coating surface, and the SEM-EDX elemental analyses on the tested specimens were conducted. The results indicate that the deterioration of the overlapping layer at the steel base-exposed portion occurs earlier than that of the single Al-5Mg thermal sprayed coating. Besides, the generation mechanism of precipitate at the steel base-exposed portion is clarified. Moreover, under the conditions of this combined cyclic corrosion test, the upper layer of heavy duty paint coating still has enough anti-corrosion performance even after the deterioration occurred at the thermal spray coating.